Japan’s big three beef bowl restaurant chains, the country’s answer to hamburger giants like McDonald’s, are in a price war. It is a sign, many people say, of the dire state of Japan’s economy that even dirt-cheap beef bowl restaurants must slash their already low prices to keep customers.

The battle has also come to epitomize a destructive pattern repeated across Japan’s economy. By cutting prices hastily and aggressively to attract consumers, critics say, restaurants decimate profits, squeeze workers’ pay and drive the weak out of business — a deflationary cycle that threatens the nation’s economy.

“These cutthroat price wars could usher in another recessionary hell,” the influential economist Noriko Hama wrote in a magazine article that has won much attention. “If we all got used to spending just 250 yen for every meal, then meals priced respectably will soon become too expensive,” she said. “When you buy something cheap, you lower the value of your own life.”

Deflation — defined as a decline in the prices of goods and services — is back in Japan as it struggles to shake off the effects of its worst recession since World War II.

While prices have fallen elsewhere during the global economic crisis, deflation has been the most persistent here: consumer prices among industrialized economies rose by a robust 1.3 percent in the year to November, but fell 1.9 percent in Japan.

In the decline, companies that undercut rivals too aggressively are being chastised as reckless at best, or as traitors undermining the country’s recovery at worst. Every markdown of beef bowl prices by the big three restaurants — Sukiya, Yoshinoya and Matsuya — has been promptly broadcast by the national news media here.

Japan has reason to be worried. Deflation hampered Japan from the mid-1990s, after the collapse of its bubble economy, to at least 2005. Households held back spending on big-ticket goods, knowing they would only get cheaper. Companies were unsure of how much to invest. At the time, the three beef bowl chains were in a similar price war.

Still, government officials back then emphasized the supposed benefits of deflation; falling prices were good for households, they said. Others said deflation would help restructure the economy by weeding out weak companies.

But the drawn-out deflationary cycle weighed heavily on Japan’s recovery. Apart from putting a damper on consumption and investment, asset deflation ravaged the country’s banks and shut out new businesses from credit.

Now that deflation is back, Japan is wary. Unemployment remains near record highs, and wages are falling. Mounting public debt is also a problem, causing Standard & Poor’s on Tuesday to cut its outlook for Japan’s sovereign rating for the first time since 2002. Japan must do more to lift its economy out of deflation and bolster long-term growth, S.& P. said.

Moreover, the population is shrinking, making demand inherently weak. Economists say Japan’s economy is saddled with a 35 trillion yen, or $388 billion, “demand gap,” or almost 7 percent of the country’s economic output.

“With supply continuing to exceed demand by a massive margin, deflationary expectations are proving very difficult to shake,” said Ryutaro Kono, an economist at BNP Paribas in Tokyo. “Households have been tightening their purse strings as the income outlook looks increasingly bleak, and we believe firms will continue to respond by lowering prices.”

Matsuya, the smallest of the three chains, set off the price war by cutting the price of its standard beef bowl to 320 yen, or $3.55, from 380 yen in early December. The market leader, Sukiya, followed suit that month, lowering its price to 280 yen, from 330 yen.

This month, the No. 2 beef bowl chain, Yoshinoya, lowered the price of its beef bowl to 300 yen, from 380 yen, though it says the cut is temporary. A smaller chain, Nakau, has also lowered prices.

The restaurant chains insist they have not downsized their portions, and will make up for cheaper prices by raising efficiency.

“We don’t consider this a price cut. We’ve simply set a new price,” said Naoki Fujita at Zensho, which runs the Sukiya chain. “With incomes falling, we needed to figure out what would be a reasonable price,” he said. “We hope customers who came every week will now come twice a week.”

In a sense, the beef bowl has always been about low prices. Yoshinoya, the beef bowl pioneer with about 1,560 stores in Japan and overseas, helped bring beef to the Japanese working class with its first restaurant in the Nihonbashi district of Tokyo in 1899.

Though beef was a delicacy at the time, Eikichi Matsuda, the Yoshinoya founder, kept prices cheap by buying in bulk, and serving as many customers as possible from his tiny stall. Speed and efficiency reigned, with workers trained to start preparing a bowl even before a customer sat down.

The same principles still apply at Yoshinoya. At a branch in central Tokyo, servers rarely take more than a minute to fill an order. The average customer spends just 7.5 minutes on a meal, and a small restaurant can serve more than 3,000 customers a day.

But forced to sell at ever-lower prices — and hurt by lower-priced competitors — making a profit has been increasingly difficult. The company suffered a 2.3 billion yen net loss in the nine months to November, and the next month, before Yoshinoya slashed prices, its sales slumped 22.2 percent. In contrast, sales at Sukiya, which serves up the cheapest beef bowl, surged 15.9 percent that month from the previous year.

Yoshinoya is not considering further price cuts. Squeezing out more savings is “like wringing a dry towel,” said a spokesman, Haruhiko Kizu.

Meanwhile, labor disputes at Sukiya show how falling prices and revenue can quickly hurt workers. A string of former workers have sued the chain over withholding overtime pay. Sukiya denies the accusations.

Other companies have been harshly criticized for slashing prices. Fast Retailing, the company behind the fast-growing Uniqlo brand, has garnered as much disapproval as awe for selling jeans as low as 990 yen. McDonald’s, on the other hand, has won kudos for resisting bargain basement prices by introducing a series of big “American-style” burgers for more than 400 yen, considered expensive in today’s Japan.

“Some Japanese companies are waging such reckless price wars, they’re wringing their own necks,” said Masamitsu Sakurai, who heads the influential business lobby Keizai Doyukai. “Companies need to be more creative. They should come up with products that add value.”

Economists say it is absurd to blame individual companies for Japan’s deflation. “For prices to fall during an economic downturn is natural. That stimulates demand and facilitates an eventual recovery,” said Takuji Aida, chief economist for UBS in Tokyo. “But this mechanism doesn’t work when there is such a big demand shortfall.”

“When prices fall because of an increase in productivity at a company, it’s good for the economy,” said Sean Yokota, an economist for UBS based in Tokyo. “It’s the demand gap that’s damaging.”

The government has vowed to lift household incomes through a series of subsidies, including new cash payments to families with small children. But the scale of government payments — 2.3 trillion yen in the case of the child subsidies — is hardly enough to fill the nation’s huge demand shortfall. With interest rates close to zero, Japan also has few options left in monetary policy.

In the meantime, cutthroat price battles are already driving laggards out of business. Wendy’s, the American burger chain, left Japan on Dec. 31.

It is not surprising, considering the competition. A mere stone’s throw from Tokyo’s celebrated Ginza district is Shokuan, the kind of restaurant that is undercutting everyone.

Shokuan, which has no chairs nor table service, is a cluster of beer vending machines huddled under the train tracks. A man behind a tiny counter sells dirt-cheap morsels: fish sausages for 50 yen, prawn crackers for 60 yen, canned yakitori for 160 yen. Many days of the week, Shokuan is spilling over with customers.

“I don’t think there’s anything around here cheaper than this. That’s why I started to come,” said Yasunori Miura, a manufacturing company employee and a recent regular. “This here,” he said, pointing to his fish sausage, “is deflation.”